The present invention relates to a method and a device for degassing a cooling system for an internal combustion engine, in which a coolant is brought to circulate partly in a cooling circuit between the engine and a radiator unit and partly between the engine and a bypass circuit past the radiator unit, the coolant flow being controlled, in dependence of the temperature, to flow through the cooling circuit and/or the bypass circuit, and the degassing being performed through draining off a limited coolant flow.
In principle, cooling systems for internal combustion engines are closed systems, in which the coolant is circulated, under a certain pressure, by the coolant pump. When filling up, and also during operation, gas pockets may occur inside the system, which is degassed continuously by means of degassing passages, which also release a small amount of coolant to an expansion reservoir. Hereby, a so-called parasite flow will occur, i.e. a non-wanted flow of coolant, which is however re-circulated, and will be pressurised again in the coolant pump. Nevertheless, due to this, the pump must be sized for a larger flow than the useful coolant flow, thus limiting the efficient capacity of the pump.
The object of the present invention is to provide a method and a device, whereby the non-useful coolant flow can be reduced.
Said object is achieved by a method and a device according to the invention, whereby degassing is obtained through draining off of a limited portion of that coolant flow which is brought to flow through the bypass circuit. Hereby it is achieved, that when the cooling requirement is at a maximum, the entire coolant flow will be directed through the radiator unit.